Process and apparatus for producing centrifugally cast metal tubes



April 7, 1964 w. W'ELZ 3,127,643 PROCESS AND APPARATUS FOR PRODUCINGCENTRIFUGALLY CAST METAL TUBES Filed May 31, 1961 J 7 ,la

7 [all 6 I. l I I I I5 INVENTOR WERNER WELZ BY mstem, m oss 6 msi'erfiUnited States Patent 3,127,643 PROCESS AND APPARATUS FQR PRODUCINGCENTRIFUGALLY CAST METAL TUBES Werner Weiz, Staifel (Lahn), Germany,assignor to Buderussche Eisenwerke, Wetziar, Germany, a

corporation of Germany Filed May 31, 1%1, Ser. No. 113,846 Claimspriority, application Germany May 31, 1960 2 Claims. (Cl. 2265) Mypresent invention relates to a device and a process for producingcentrifugally cast metal tubes and, more particularly, forsimultaneously producing two centrifugally cast iron tubes eachterminating in a bell at one end.

It is an object of the present invention to provide a device and aprocess for the production of faultless centrifugally cast metal tubessuitable for sewage lines, water and gas distribution systems, and thelike.

It is another object of the present invention to provide a device inwhich such tubes can be serially manufactured in a highly economicalmanner designed to simplify the problem of maintenance betweenproductive cycles and to minimize the cleaning and trimming operationsrequired.

It is a further object of the present invention to provide a device anda process insuring a clean separation between a pair of tubular memberscast in a single centrifugal operation.

In accordance with the invention I provide a tubular casting mold openat both ends and rotatable about a horizontal axis, these ends beingpreferably flared to form bell terminations on the metal bodies to bemolded therein, in combination with stationary inlet means forintroducing liquid metal into the mold at one end. At an intermediatelocation the mold is formed with an annular obstruction, e.g. as anintegral ridge or as an insertable ring, of a height which is a smallfraction of the inner mold radius but at least equal to the wallthickness of the finished castings so that they become separated fromeach other during the centrifuging process; this separation shouldoccur, at the latest, during shrinkage of the metal in the final orcooling stage of the process. The introduction of the molten metal maytake place through one of the two terminal mold cores which are insertedinto the flared ends to define the bell recesses at the female ends ofthe castings; advantageously, for this purpose, a feed pipe is insertedthrough such mold core at the inlet end of the mold so as to extend fromthe metal injector to a point just beyond this mold core. The quantityof molten metal introduced into the centrifugal chamber, i.e. into theinterior of the rotating mold, should be suiiicient to insure that theannular obstruction will initially be overflown freely by the metalwhereby the latter is distributed to substantially uniform depth in thetwo chamber sections formed on opposite sides of this obstruction.

According to a more specific feature of the present invention, the innercylindrical portions of the mold on both sides of the separator ring canbe of slightly different diameters, preferably with the section havingthe smaller diameter located at the side of the mold at which the moltenmetal is introduced, the difference in the height of opposite sides ofthe ring improving its separating effect. Even a small difference ofdiameters, e.g. within the tolerances admissible for tubes of the samenominal dimensions, has a marked effect on easing the otherwise strictrequirements as to the exact amount of introduced metal.

The above, and other objects, advantages and features of my presentinvention will be better understood from the following description,given with reference to an accompanying drawing in which:

3,127,643 Patented Apr. 7, 1964 FIG. 1 is a longitudinal sectional viewof a device according to the present invention; and

FIGS. 2, 3 and 4 are fragmentary sectional views of different types ofseparator rings as utilized in the above device.

FIG. 1 shows a hollow, elongated metal mold 1 having a cylindricalhorizontally disposed through-going bore 15 and diverging at both endsinto bell-shaped sockets 16. A separator ring 6, rigid with mold 1,protrudes inwardly from the periphery of the bore 15 at an intermediatelocation between sockets 16, thereby dividing bore 15 into two sectionsfor the molding of two tubular castings 7, 8. Two tubular cores 4, 4',each with a flange 18 fitting into a respective groove at one of themold faces, extend for a short distance into the bore 15 to define withits flared extremities a form for a tube bell 3.

An inlet tube 5 of slightly frustoconical configuration so as to divergeradially from right to left as shown in FIG. 1, traverses the actualchannel of right-hand core 4 and with its enlarged end extends a shortdistance beyond that core into bore 15. The tube 5 is provided at itsprojecting extremity with a threaded portion 10 rigid with a grip bar 11which may be welded to the tube. A bent bifurcate holder 9, firmlyfastened to a sleeve 19 surrounding the tube portion 10 in threadedengagement therewith, is welded to a collar 21 having bayonet teeth 22entering mating slots 20 along the outer periphery on the right-handside of the mold 1. A stationary injector 2, schematically representedby dot-dash lines, is used for introducing molten iron into tube 5 andthence into mold 1. Rotation of grip 11 threads tube 5 into sleeve 19,thereby pressing a shoulder 12 on the tube against flange 18 of core 4to lock the latter in position. The other core 4', which may beremovably held in place by similar means not shown, provides an overflowoutlet for any excess metal capable of clearing the mouth of this core.

The mold is rotated around its longitudinal axis, during the centrifugalcasting by mechanism shown sche matically as a motor 25 having a pinion26 in mesh with gear teeth 17 on mold 1; the mold body is rotatablysupported by suitable bearing means such as roller 27.

The separator ring 6 illustrated in greater detail in FIG. 2 is oftrapezoidal cross-section and integral with mold 1; the portions of bore15 on both sides of the ring 6 have equal diameters and, if desired, thesame length. While this arrangement enables the simultaneous casting oftubes of identical cross-section, it may lead to the formation of a burr13 which must be subsequently removed. This inconvenience is largelyavoided by increasing the depth of one flank of the separator ring asshown in FIGS. 3 and 4.

In FIG. 3 the ring 6, separating two tubes 7' and 8' of slightlydifferent diameters, has flanks of unequal heights, designated h and h Asimilar arrangement is shown in FIG. 4 wherein a detachable separatorring 6" of trapezoidal cross-section overlies the step 14 between theaxially separated parts of mold 1 and is provided with a depression 23on its outer face for a fastening bolt 24 radially threaded into thewall of mold 1. The height I1 of the distal face of ring 6' or 6" asseen from the inlet (5) may be so small as to afiord a smooth passage ofthe molten metal over this ring, the separation between casting 7', 8being nevertheless insured by the larger height h of the proximal face.Ring 6' can, of course, be readily removed for repair or replacement,e.g. for purposes of adapting the mold for the casting of tubes ofdifferent thickness. It will be apparent that such detachability mayalso be provided for symmetrical rings such as the one shown in FIGS. 1and 2.

The centrifugal casting device according to the invention operates inthe following manner: Molten metal is introduced into mold 1 by theinjector 27 With mold 1 set into rotation by motor 25, the metal spreadsalong the walls of bore 15. The amount of injected metal is such thatthe molten metal passes over the separator ring 6,

.6 or 6" and spreads equally along both sides of the mold 1, therebyfilling the cavities for the bells 3. As

themetal cools, the tubular layer formed by it along the mold wallshrinks so that the ring 6 separates the resulting casting into the twoportions 7 or 7 and 8 or 8', each with a bell termination 3. These tubescan be pulled out of the mold 1 after the cores 4, 4 have been .removed,whereupon the mold 1 can be used for further casting;

The invention as described admits many modifications .readily apparentto persons skilled in the art, as for instance the application ofinjectors from both sides of the mold simultaneously, and/ or theoptional provision of means for cooling the mold (e.g. by Water).modifications are, therefore, intended to be included with- Such in thescope of the invention as defined by the appended claims.

I claim:

1. An apparatus for centrifugally casting pairs of metal tubes,comprising a tubular mold rotatable about a substantially horizontalaxis and having a bore extending along said axis, said bore having twoopen ends; stationary inlet means at one of said open ends forintroducing'a molten metal into said bore, said bore being prohaving thesmaller diameter being disposed between said l inlet means and saidridge with the section having the larger diameter being disposed beyondsaid ridge remote from said inlet means, said ridge having flanks ofdifferent height rising respectively from said sections with the flankhaving the smallest height facing said inlet means; and drive means forrotating said mold about said axis.

2. An apparatus for centrifugally casting pairs of metal tubes,comprising a tubular mold rotatable about a substantially horizontalaxis and having a bore extending along said axis, said bore having twoopen ends; stationary inlet means at one of said open ends forintroducing a molten metal into said bore, said bore being providedintermediate said openings with two adjacent generally cylindricalsections of diiferent diameter forming an annular step at theirjunction; a ring centered on said axis and seated against said step,said ring forming an'annular ridge intermediate said sections projectinginwardly beyond the walls of said sections a fraction ofthe radius ofsaid bore, the section having the smaller diameter being disposedbetween said inlet means and said ridge with the section having thelarger diameter being disposed beyond said ridge remote from said inletmeans, said ring having flanks of diflerent height rising respectivelyfrom said sections with the flank having the smallest height facing saidinlet means; locking means for removably fixing said ring axially alongsaid bore; and drive means for rotating said mold about said axis.

References Cited in the file of this patent UNITED STATES PATENTS1,551,590 Stresau Sept. 1, 1925 1,678,633 Burchartz July 31, 19281,795,637 Carrington Mar. 10. 1931

1. AN APPARATUS FOR CENTRIFUGALLY CASTING PAIRS OF METAL TUBES,COMPRISING A TUBULAR MOLD ROTATABLE ABOUT A SUBSTANTIALLY HORIZONTALAXIS AND HAVING A BORE EXTENDING ALONG SAID AXIS, SAID BORE HAVING TWOOPEN ENDS; STATIONARY INLET MEANS AT ONE OF SAID OPEN ENDS FORINTRODUCING A MOLTEN METAL INTO SAID BORE, SAID BORE BEING PROVIDEDINTERMEDIATE SAID OPENINGS WITH TWO ADJACENT GENERALLY CYLINDRICALSECTIONS OF DIFFERENT DIAMETER AND AN AXIALLY FIXED ANNULAR RIDGEINTERMEDIATE SAID SECTIONS, SAID RIDGE PROJECTING INWARDLY BEYOND THEWALLS OF SAID SEC-